The invention relates to vent tubes for axles, and in particular to an axle vent tube for heavy-duty vehicles such as semi-trailers. More particularly, the invention is directed to a tube formed in a generally circular configuration and which is disposed about and substantially surrounds a hollow axle, so that one end of the tube is tapped into the axle and the opposite end of the tube includes a valve, whereby pressure build-up in the vehicle axle and wheel hub is released while preventing contaminants from entering the axle and hub through the tube, thereby extending the life of the hub seals and wheel bearings themselves.
Automatic tire pressure inflation systems for commercial heavy vehicles such as semi-trailers and full trailers have grown in popularity in recent years. To meet the demand, numerous suppliers have introduced tire inflation systems having various designs. One such design approach is to run an air pressure supply line through the hollow axle to feed a rotary union located at the end of the axle spindle or wheel hubcap. The rotary union is an airtight rotating seal that enables fluid communication between the non-rotating axle and the rotating tire. Failure of the supply line or rotary union typically causes a sudden air pressure build-up in the hollow axle and wheel hub, which if left unrelieved, can lead to wheel hub seal failure. Such seal failure in turn usually leads to a loss of bearing lubrication and subsequent rapid wheel bearing failure, resulting in an expensive repair. Also, even a small increase in pressure from a slow leak inside the axle or hub can greatly reduce the hub seal life.
Many of the aforementioned tire inflation systems incorporate a venting device or system in the wheel hubcap to relieve such excess pressure. However, many of these hubcap venting systems lack the robustness to adequately prevent contaminants from entering the hub, thus failing to offer adequate protection to the bearing lubricant and bearings. More particularly, due to the exposed location of these hubcap venting systems on the vehicle, contaminants such as water from a high-pressure truck wash have been known to breach many of these prior art hubcap venting systems.
Other known prior art axle vent systems or devices include drive axle vent tubes which are installed by tapping one end of a tube or hose into the axle and allowing the tube to hang vertically from the axle, with the opposite end of the hose being open to atmosphere. Vent tubes are needed on drive axles because the gears inside the axle generate heat during operation, thus causing the air inside the axle to expand. However, such a device is less than efficient in preventing contaminants, such as water, from entering the axle. Another known prior art axle vent system involves tapping one end of a rubber hose or tube usually into the top central portion of an axle, and fastening the hose in a manner, such as to the vehicle frame, that allows the hose to extend vertically upwardly from the axle, bend at its highest point and then wrap back upon itself vertically downwardly. Others of this type of vent tube are free-standing and the downwardly-extending portion of the tube simply is secured in some manner, such as with a common tie wrap, to the upwardly-extending portion. Again, however, the end of the hose opposite from the end tapped into the axle is open and is inadequate in preventing contaminants from entering the axle. For example, if a semi-trailer having such an axle vent device backed into a dock which was partially submerged in water and the axle vent tube became submerged, water could enter the axle. Also, its typical location at the central portion of the axle makes it susceptible to damage or even being ripped off of the axle by flying debris or the like during operation of the vehicle. The risk of damage is especially high for the freestanding type of vent tube, and is even subject to damage from the force of the wind it encounters during vehicle operation. The top of the axle at any location between the suspension assembly attachment points, that is, generally the central portion of the axle, also is a relatively high-stress portion of the axle, and drilling a hole at that location could undesirably weaken the axle which could lead to further axle damage or even axle failure. This is particularly true on a trailing arm-type suspension assembly where the axle supplies the auxiliary roll stiffness for the suspension assembly.
Applicant has solved the above-noted problems with its axle vent tube of the present invention, which preferably utilizes a tube preformed into at least a single loop capable of substantially surrounding the axle, and having an inside diameter slightly smaller than the outside diameter of the axle. The tube preferably is formed of a material so that when stretched around the axle and released, it firmly grips the axle, thus eliminating the need for fastening hardware. One end of the tube is plumbed to an opening formed in the axle and communicates with the hollow axle interior, and the opposite end of the tube includes a one-way check valve or duck bill which communicates with atmosphere, the latter of which being well-known in the valve art. The valve allows pressure build-up in the axle to vent while preventing contaminants from entering the axle and wheel hub through the vent tube. The circular disposition of the tube about the axle also aids in preventing contaminants from entering the axle because portions of the tube are vertically disposed, and gravity thus operates to assist in preventing travel of contaminants through the tube and into the axle interior, which is especially important if the duck bill should fail for any reason. The vent tube is protected from damage by disposing it on the axle at a protected location within the suspension assembly beam, thus eliminating the need for add-on shields and the like, and at a low-stress location on the axle itself.
Objectives of the present invention include providing a vent tube for a vehicle axle which is capable of venting undesirable excess pressure from the axle and wheel hub.
Another objective of the present invention is to provide such an axle vent tube which prevents contaminants from entering the axle.
An additional objective of the present invention is to provide such an axle vent tube which is protected by existing vehicle structures to minimize the possibility of damage to and/or failure of the tube.
Still a further objective of the present invention is to provide such an axle vent tube which is simple, economical, lightweight, durable in use, and easy to install, maintain, and replace.
These objectives and advantages are obtained by the vehicle axle vent tube of the present invention, the general nature of which can be stated as including a device for venting to atmosphere built-up air pressure from a hollow vehicle axle and a wheel hub, the device including a conduit having first and second ends, at least a portion of the conduit being vertically oriented, means for mounting the conduit first end on the axle to create fluid communication between the axle hollow interior and the conduit, and means disposed on the conduit second end to enable flow of the built-up air pressure to atmosphere and to substantially prevent ingress of contaminants into the axle and the hub.